Biological field and laboratory methods for measuring the quality of ...
Biological field and laboratory methods for measuring the quality of ...
Biological field and laboratory methods for measuring the quality of ...
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BIOLOGICAL METHODS<br />
Because <strong>of</strong> <strong>the</strong> small area sampled, data from<br />
corin g devices are likely to provide very<br />
imprecise estimates <strong>of</strong> <strong>the</strong> st<strong>and</strong>ing crop <strong>of</strong><br />
macrobenthos. As <strong>the</strong> data in Table 3 illustrate,<br />
<strong>the</strong> variability in numbers <strong>of</strong> oligochaetes (a<br />
dominant component <strong>of</strong> <strong>the</strong> fauna studied)<br />
collected in corers is similar to that <strong>for</strong> grab-type<br />
devices; however, <strong>the</strong> corer data were calculated<br />
from two to three times as many replicate<br />
samples <strong>and</strong> were collected from a relatively<br />
homogeneous substrate.<br />
Such additional replication with corers is<br />
feasible because <strong>of</strong> <strong>the</strong> small amount <strong>of</strong> material<br />
per sample that must be h<strong>and</strong>led in <strong>the</strong><br />
<strong>laboratory</strong>. Multiple-head corers have been used<br />
in an attempt to reduce <strong>the</strong> <strong>field</strong> sampling ef<strong>for</strong>t<br />
that must be expended to collect large series <strong>of</strong><br />
core samples (19).<br />
The Dendy inverting sampler (57) is a highly<br />
efficient coring-type device used <strong>for</strong> sampling at<br />
depths to 2 or 3 meters in nonvegetated substrates<br />
ranging from s<strong>of</strong>t muds through coarse<br />
s<strong>and</strong>. Because <strong>of</strong> <strong>the</strong> small surface area sampled,<br />
data obtained by this sampler suffer from <strong>the</strong><br />
same lack <strong>of</strong> precision (51) as <strong>the</strong> coring devices<br />
described above. Since <strong>the</strong> per-sample processing<br />
time is reduced, as with <strong>the</strong> corers, large series <strong>of</strong><br />
replicates can be collected. The Dendy sampler<br />
is highly recommended <strong>for</strong> use in habitats <strong>for</strong><br />
which it is suitable.<br />
Stovepipe-type devices include <strong>the</strong> Wilding<br />
sampler (2, 57) <strong>and</strong> any tubular material such as<br />
60 to 75 cm sections <strong>of</strong> st<strong>and</strong>ard l7-cmdiameter<br />
stovepipe (51) or 75 cm sections <strong>of</strong><br />
30-cm-diameter aluminum irrigation pipe fitted<br />
with h<strong>and</strong>les. In use, <strong>the</strong> irrigation pipe or commercial<br />
stovepipe is manually <strong>for</strong>ced into <strong>the</strong><br />
substrate, after which <strong>the</strong> contained vegetation<br />
<strong>and</strong> coarse substrate materials are removed by<br />
h<strong>and</strong>. The remaining materials are repeatedly<br />
stirred into suspension, removed with a longh<strong>and</strong>led<br />
dipper, <strong>and</strong> poured through a woodenframed<br />
floating sieve. Because <strong>of</strong> <strong>the</strong> laborious<br />
<strong>and</strong> repetitive process <strong>of</strong> stirring, dipping, <strong>and</strong><br />
sieving large volumes <strong>of</strong> material, <strong>the</strong> collection<br />
<strong>of</strong> a sample <strong>of</strong>ten requires 20 to 30 minutes.<br />
The use <strong>of</strong> stovepipe samplers is limited to<br />
st<strong>and</strong>ing or slowly moving waters having a<br />
maximum depth <strong>of</strong> less than 60 cm. Since<br />
10<br />
problems relating to depth <strong>of</strong> sediment penetration,<br />
changes in cross-sectional area with depth<br />
<strong>of</strong> penetration, <strong>and</strong> escapement <strong>of</strong> organisms are<br />
circumvented by stovepipe samplers, <strong>the</strong>y are<br />
recommended <strong>for</strong> quantitative sampling in all<br />
shallow water benthic habitats. They probably<br />
represent <strong>the</strong> only quantitative device suitable<br />
<strong>for</strong> sampling shallow-water habitats containing<br />
st<strong>and</strong>s <strong>of</strong> rooted vascular plants <strong>and</strong> will collect<br />
organisms inhabiting <strong>the</strong> vegetative substrates as<br />
well as those living in sediments. The coefficients<br />
<strong>of</strong> variation <strong>for</strong> <strong>the</strong> stovepipe samples in<br />
Table 3 are comparable to <strong>the</strong> coefficients <strong>for</strong><br />
grab samples, although <strong>the</strong> stovepipe samples<br />
were collected in heavily vegetated <strong>and</strong> consequently<br />
highly variable habitats.<br />
3.3.4 Artificial substrates<br />
The basic multiple-plate sampler (23) <strong>and</strong><br />
rock-filled basket sampler (21) have been<br />
modified by numerous workers (17, 40) <strong>and</strong> are<br />
widely used <strong>for</strong> investigating <strong>the</strong> macroinvertebrate<br />
community. Both samplers may be<br />
suspended from a surface float or may be<br />
modified <strong>for</strong> use in shallow streams by placing<br />
<strong>the</strong>m on a rod that is driven into <strong>the</strong> stream<br />
bottom or anchored in a piece <strong>of</strong> concrete (24).<br />
A multiple-plate sampler similar to that<br />
described by Fullner (17), except with circular<br />
plates <strong>and</strong> spacers, is recommended <strong>for</strong> use by<br />
EPA biologists. This sampler is constructed <strong>of</strong><br />
0.3-cm tempered hardboard cut into 7.5-cm<br />
diameter circular plates <strong>and</strong> 2.5-cm circular<br />
spacers. A total <strong>of</strong> 14 plates <strong>and</strong> 24 spacers are<br />
required <strong>for</strong> each sampler. The hardboard plates<br />
<strong>and</strong> spacers are placed on a Y4-inch (0.625 cm)<br />
eyebolt so that <strong>the</strong>re are eight single spaces, one<br />
double space, two triple spaces, <strong>and</strong> two<br />
quadrupIe spaces between <strong>the</strong> plates. This<br />
sampler has an effective surface area (excluding<br />
<strong>the</strong> bolt) <strong>of</strong> 0.13 square meter <strong>and</strong> conveniently<br />
fits into a wide-mouth glass or plastic jar <strong>for</strong><br />
shipment <strong>and</strong> storage. Caution should be<br />
exercised in <strong>the</strong> reuse <strong>of</strong> samplers that may have<br />
been subjected to contamination by toxicants,<br />
oils, etc.<br />
The rock basket sampler is a highly effective<br />
device <strong>for</strong> studying <strong>the</strong> macroinvertebrate<br />
community. A cylindrical, chromeplated basket